Add holoviews agent

[ahuang11]

Resolves #1231

More fixes to translate.py, prevent nested models from being streamed (since the model seems to switch between correct models then wrong models between each chunk), adds a base view between hvPlotView and HoloViewsView

[ahuang11]

HoloViewsAgent now works in Lumen after changing | to Union[..., None] in the translator while that's being fixed in instructor.

Then, I found a bunch of edge cases in the translator where pet = param.ClassSelector(class_=(Dog, Cat)) wasn't properly translating to pet: Union[Dog, Cat], handling instantiate=False and proposed that we migrate translate.py to param https://github.com/holoviz/param/issues/828#issuecomment-2878253054

Just need to wrap up translating operations and fixing those warnings

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 67.27273% with 144 lines in your changes missing coverage. Please review.

Project coverage is 57.04%. Comparing base (4b47e4f) to head (25d05f1).

Files with missing lines	Patch %	Lines
lumen/ai/translate.py	71.32%	82 Missing :warning:
lumen/views/base.py	68.53%	28 Missing :warning:
lumen/ai/agents.py	20.58%	27 Missing :warning:
lumen/ai/llm.py	0.00%	7 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1233      +/-   ##
==========================================
- Coverage   57.07%   57.04%   -0.04%     
==========================================
  Files         113      113              
  Lines       17612    17810     +198     
==========================================
+ Hits        10052    10159     +107     
- Misses       7560     7651      +91     

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